Cocaine is such a hard habit to kick, especially if it has gotten to the level of severity you are describing. At this point, I think it not only would be more successful, but a lot safer if you reached out for professional help. If you live in America and are of the Christian faith, or would be willing to accept Jesus into your life for the sake of recovery, feel free to check out
Teen Challange USA. If not, you can try contacting
To Write Love On Her Arms for more information on where to go. If you're stressed about the cost, there are a lot of places that stay free because of donations received.
If you would rather not go away from home, Narcotics Anonymous is always an option!